xml-dev - RE: XML over HTTP: SOAP and ...?

[Mark Birbeck <Mark.Birbeck@iedigital.net>]

Robert DuCharme wrote:
> (from David Megginson's "Random XTech observations)
> >6. Everyone wants to send XML over HTTP.  Nothing new there, but I'd
> >   like to see some kind of interoperable, critical mass emerge,
> >   whatever the flavour.
> 
> When a DCOM-oriented colleague asked me about SOAP, I did some quick
> research to find out the basics. While a heavily Microsoft-backed
> proposed standard often means that there's a non-Microsoft alternative
> out there, I didn't see any alternative to SOAP. I gather from
> http://www.develop.com/soap/soapfaq.htm#22 that xml-rpc cooperates
with
> SOAP more than it competes with it, although I may have misunderstood
this.

XML-RPC is a precursor to SOAP, but is not backwards compatible. An
XML-RPC server would not understand a SOAP payload. The FAQ you have
read refers to SOAP's origins, not its current state. (Note also with
that document, that there were quite important changes from SOAP 0.9 to
1.0, so make sure you read the 'Updated!' bit at the end

SOAP is a much better spec though. If I may be so crass as to plug
Wrox's Professional XML book; I have contributed the section on SOAP in
chapter 11. It goes into quite a lot of detail looking at the
improvements that SOAP made on XML-RPC. The section also walks you
through an ASP version of the client and server code, and I believe a
download is available from Wrox's site. If not, I can post it to the
list if you're interested.

> After reading the above comment from David, I wondered: what 
> other flavors are out there?

In the space you are talking of I only know of XML-RPC and SOAP. I would
regard them as general purpose RPC mechanisms, of which SOAP is the
better one. However, WebDAV also uses HTTP to convey XML formatted
instructions, but they come from a specified range of valid commands to
allow editing of objects and their meta-data. As a complimentary spec,
DASL allows them to be queried.

The main difference here is that you could write a SOAP implementation
in a weekend - you couldn't do the same for WebDAV!

Best regards,

Mark Birbeck
x-port.net

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